I. Field of the Invention
This invention relates to steering skis used for snowmobiles and similar vehicles intended to travel over snow and ice.
II. Background Art
Snowmobiles and similar vehicles are generally provided with a pair of skis at their front ends intended to support the vehicles without sinking unduly into the snow and also intended to provide steering when turned from side to side.
Conventionally, a steering ski of this kind has a generally flat lower surface, usually provided with an elongated central downward projection (often referred to as a keel) extending from the lower surface and intended to dig into the snow below the ski in order to resist lateral sliding when the vehicle is turning. The front end of such a ski usually has an upturned pointed tip to ensure that the ski rides on the snow rather than becoming buried deeply in it.
A disadvantage of conventional steering skis is that they usually cannot be turned in deep snow at high speed without a considerable risk of uncontrollably tipping the vehicle completely over. This is because the lateral edge of the leading ski may dig into the snow rather than ride over it. As the vehicle turns, the extra drag caused by the angled skis produces a braking action which rolls the vehicle to the outside of the curve and this tends to make the leading edge of the leading ski dig more deeply into the snow. Naturally, this introduces a considerable element of danger, particularly for inexperienced riders.
Wayne L. Warnke in U.S. Pat. No. 4,491,333 issued on Jan. 1, 1985 disclosed a ski which is said to have improved turning performance. The Warnke ski has upward flares provided along both lateral edges of the skis to create a lifting force on the ski during turning. As explained in the Warnke patent (Column 2, lines 46 to 50 and the drawings), the flare at the edges of the ski is formed by a flat surface extending abruptly upwardly and outwardly from the lower surface of the ski at an angle of 30.degree.-60.degree., and preferably at about 45.degree..
Despite the improvement claimed by Warnke, we have found that steering skis of this kind still suffer from poor performance during turning. The skis tend to throw up a great deal of snow during turning, which affects visibility and produce a considerable amount of drag. This drag creates a braking action on the machine which results in additional weight transfer to the outside ski which in turn counteracts the lift the ski is trying to create. As a result, skis of this kind offer very little improvement in practice over conventional skis.